After a thorough review of the proposed transactions, the Antitrust Division has determined that each acquisition is unlikely to substantially lessen competition and has closed these three investigations. In all of the transactions, the division conducted an in-depth analysis into the potential ability and incentives of the acquiring firms to use the patents they proposed acquiring to foreclose competitors. In particular, the division focused on standard essential patents (SEPs) that Motorola Mobility and Nortel had committed to license to industry participants through their participation in standard-setting organizations (SSOs). The division's investigations focused on whether the acquiring firms could use these patents to raise rivals' costs or foreclose competition. The division concluded that the specific transactions at issue are not likely to significantly change existing market dynamics.

The agency said its concerns about the potential anticompetitive use of the standard essential patents was "lessened by the clear commitments by Apple and Microsoft to license SEPs on fair, reasonable and non-discriminatory terms," the statement said.

The partnership group, which the DOJ called the Rockstar Bidco consortium, purchased Nortel's remaining patent portfolio--about 6,000 patents and patent applications--in a bankruptcy auction last year for $4.5 billion. The group also includes EMC, Ericsson, and Sony.

Separately, Apple has proposed acquiring patents held by CPTN Holdings that were formerly owned by Novell. CPTN acquired the patents in April of last year on behalf of Apple, Oracle. and EMC. "As a member of the Open Invention Network (OIN), Novell committed to cross-license its patents on a royalty-free basis for use in the open source 'Linux system,'" the DOJ statement said.